1. Field of the Invention
The present invention relates to a process for the manufacture of anti-abradant elements for devices with two parts moving against one another, especially a rotating part and a stator, as well as an anti-abradant element manufactured according to this process.
2. Description of the Prior Art
The degree of effectiveness of turbines, compressors, pressure shaft equipment, etc. decreases with increasing play between rotor and stator. Hence, attempts are always made to reduce the clearance between the rotor on the one hand, and the stator on the other, to the minimum. Optimum play is determined by material characteristics, manufacturing technology, and the size of the rotor and the stator as well as operating conditions to which the machine is subjected.
In order to keep the play between rotor and stator to a minimum, it has been suggested to equip the rotor vanes with a sharpened edge at the head. Thus, as the vanes touch the stator, the sharpened vane edges are bent or worn down so that harmful abrasion does not occur.
Further, in order minimum, reduce the play between rotor and stator to a ninimum, it has been suggested to cover the inside stator walls with a relatively soft layer which can be worn down, gradually, by the touching rotor vanes. Such layers consist of, for example, graphite, die-cast or sintered porous nickel-chromium alloys or nickel-chromium materials, honeycomb cells etc.; they are referred to as anti-abradants subject to abrading. In each case the aim was to make these anti-abradant layers as constant as possible with regard to shape so that no growth manifestations occur because of environmental temperature and/or environmental atmosphere.
These processes are deficient because the soft layers or the sharpened vane edges are subjected to an irreversible change in shape as the result of abrasion in that they are either bent or worn down. Additional factors are corrosion and erosion of the vane edges or the cell wall edges and the stator wall so that during continuous operation the play between rotor and stator increases steadily and the degree of effectiveness of the machine decreases.